Discfish, Diretmus argenteus Johnson 1864


Other Names: Little Dory, Silver Spinyfin, Silver Spinyfish, Spinyfin, Spiny-fin

The aptly named Discfish, Diretmus argenteus, from a seamount in the Tasman Sea, May 2003. Source: Robin McPhee & Mark McGrouther / NORFANZ Founding Parties. License: All rights reserved

Summary:

A laterally compressed almost circular spinyfin with a bright silver body, a dark back and caudal-fin base, and a ridge of bony scutes along the ventral surface immediately before pelvic-fin bases, and the anus immediately before the anal-fin origin.


Cite this page as:
Bray, D.J. 2018, Diretmus argenteus in Fishes of Australia, accessed 17 Nov 2018, http://fishesofaustralia.net.au/home/species/1398

Discfish, Diretmus argenteus Johnson 1864

More Info


Distribution

Off Moreton Bay, Queensland, to the South Tasman Rise off Tasmania, around southern to west of Broome, Western Australia; also on seamounts, ridges and rises in the Tasman Sea. Elsewhere the species is circumglobal in tropical and temperate waters, except for the northern Pacific. Juveniles are mesopelagic, while large adults are benthopelagic.

Features

Dorsal fin 25-29; Anal fin 18-24; Caudal fin 19; Pectoral fin 16-20; Pelvic fin i, 6; Gill rakers 17-24.

Body very deep (60-89% SL), compressed, almost circular in profile; caudal peduncle shallow; anus immediately before anal-fin origin. Head moderately large (34-48% SL), with prominent bony ridges and deep mucous cavities; eyes large; mouth large, oblique, extending to below rear half of eye, tip of lower jaw a blunt, angled bony point; narrow band of small sharp, fine teeth in both jaws.

Scales finely ctenoid, deciduous, covering body including nape and cheeks on head; abdominal surface between anus and underside of head with scutes; lateral line absent. 

A single moderately long-based low dorsal fin, extending over rear half of body; anal fin opposite, similar to dorsal fin but with a shorter base; each dorsal and anal fin ray with large laterally projecting spine on either side near base, series of smaller spines further up; caudal fin large, forked, each ray with series of small laterally projecting spines on either side. Pectoral fins angular, moderately large, rays with small spines on outer surfaces. Pelvic fins thoracic, angular, moderately large, fin “spine” with numerous small laterally projecting spines on outside edge, rays with smaller spines ventrally.

Colour

Silvery, with underlying brown pigment, especially dorsally and ventrally; bases of dorsal, anal and caudal fins dark brown; interior of mouth and gill cavities black.

Feeding

Carnivore - feeds on zooplankton, especially pelagic crustaceans. Discfish are preyed upon by large pelagic predators such as tunas, Swordfish, lancetfishes, dolphins and whales.

Biology

The eggs and larvae are pelagic.

Fisheries

Taken as bycatch in trawl fisheries.

Remarks

Discfish undertake daily vertical migrations and their enormous eyes have remarkably specialised retinas that provide enhanced vision in the bluish-green light at mesopelagic depths.

Similar Species

Differs from the Black Spinyfin, Diretmichthys parini, in having a ridge of bony scutes along the ventral surface before the pelvic-fin bases (vs. no ridge of bony scutes before the pelvic fin bases), and the anus positioned immediately in front of the anal-fin origin (vs. anus about halfway between the bases of the anal and pelvic fins).

Species Citation

Diretmus argenteus Johnson 1864, Proc. Zool. Soc. Lond. 1863(3): 403403, pl. 36(1). Type locality: off Madeira.

Author

Bray, D.J. 2018

Resources

Australian Faunal Directory

Discfish, Diretmus argenteus Johnson 1864

References


Bray, D.J. 2008. Family Diretmidae; Spinyfins. pp. 431-432 in Gomon, M.F., Bray, D.J. & Kuiter, R.H. (eds). Fishes of Australia's Southern Coast. Sydney : Reed New Holland 928 pp. 

Campbell, W.D. 1879. On a new fish. Transactions of the New Zealand Institute 11: 297-298 

Cohen, D.M. (ed.) 1973. Fishes of the western North Atlantic. Halosuriforms, Killfishes, Squirrelfishes and other Beryciforms, Stephanoberyciforms, Grenadiers. Yale University : The Sears Foundation of Marine Research Memoirs I Pt 6 698 pp.

Denton, E.J. 1990. Light and vision at depths greater than 200 metres, pp. 127-148. In Herring P.J., Campbell A.K., Whitfield M. & Maddock L. (eds) Light and Life in the Sea. Cambridge University Press, Cambridge, 368 pp.

Denton, E.J. & Locket, N.A. 1989. Possible wavelength discrimination by multibank retinae in deep-sea fishes. Journal of the Marine Biological Association of the United Kingdom 69: 409-435. 

Glover, C.J.M. 1994. Families Diretmidae, Melamphaeidae. pp. 412-416 figs 370-372 in Gomon, M.F., Glover, C.J.M. & Kuiter, R.H. (eds). The Fishes of Australia's South Coast. Adelaide : State Printer 992 pp. 810 figs.

Gomon, M.F., Glover, C.J.M. & Kuiter, R.H. (eds) 1994. The Fishes of Australia's South Coast. Adelaide : State Printer 992 pp. 810 figs.

Iwamoto, T. 2015. Diretmus argenteus. The IUCN Red List of Threatened Species 2015: e.T18124015A42461403. http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T18124015A42461403.en. Downloaded on 12 November 2017.

Johnson, J.Y. 1864. Descriptions of three new genera of marine fishes obtained at Madeira. Proceedings of the Zoological Society of London 1863(3): 403-410 pl. 36 Ref available at BHL

Koslow, J.A., Bulman, C.M.& Lyle, J.M. 1994. The mid-slope demersal fish community off southeastern Australia. Deep-sea Research 41: 113-141.

Kotlyar, A.N. 1988. Classification and distribution of fishes of the family Diretmidae (Beryciformes). Journal of Ichthyology 28(2): 1-15.

Munk, O. 1966. On the retina of Diretmus argenteus Johnson 1863 (Diretmidae, Pisces). Videnskubelige Meddelelser fra Dansk Naturhistorik Forening i Kjobenhavn 129: 73-80. 

Munk O. 1982. Cones in the eye of the deep-sea teleost Diretmus argenteus. Vision Research 22(1): 179–181.

Paxton, J.R. 1999. Families Gibberichthyidae, Rondeletiidae, Barbourisiidae, Cetomimidae, Mirapinnidae, Megalomycteridae, Anoplogastridae, Diretmidae. pp. 2203-2211 in Carpenter, K.E. & Niem, T.H. (eds). The Living Marine Resources of the Western Central Pacific. FAO Species Identification Guide for Fisheries Purposes. Rome : FAO Vol. 4 pp. 2069-2790.

Post, A. & Quéro, J.C. 1981. Revision des Diretmidae (Pisces, Trachichthyoidei) de l'Atlantique avec description d'un noveau genre et d'une nouvelle espèce. Cybium 3 5(1): 33-60 figs 1-11 

Roberts, C.D. 2015. Families Anoplogastridae, Diretmidae and Monocentridae. pp. 1002-1008, in Roberts, C.D., Stewart, A.L. & Struthers, C.D. The Fishes of New Zealand. Wellington : Te Papa Press Vol. 3 pp. 577-1152.

Watson, W. 1996. Diretmidae: spinyfins. pp. 679-681 in Moser, H.G. The early stages of fishes in the California Current region. Fisheries Investigations Atlas No. 33 Lawrence, Kansas : California Cooperative Oceanic Allen Press, Inc. 1505 pp.

Young, J.W.,  Lamb, T.D. & Bradford, R.W. 1996. Distribution and community structure of midwater fishes in relation to the subtropical convergence off eastern Tasmania, Australia. Marine Biology 126(4): 571-584.

Quick Facts


CAAB Code:37254002

Conservation:IUCN Least Concern

Depth:300-1275 m

Habitat:Mesopelagic, benthopelagic

Max Size:13 cm SL

Species Image Gallery

Species Maps

CAAB distribution map